#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import absolute_import, print_function, division

import math
import re
import sys
import inspect
from time import time
import datetime
from dateutil.relativedelta import relativedelta
from dateutil.tz import tzutc
import calendar
import binascii
import random

try:
    from collections import OrderedDict
except ImportError:
    OrderedDict = dict  # py26 degraded mode, expanders order will not be immutable

step_search_re = re.compile(r'^([^-]+)-([^-/]+)(/(\d+))?$')
only_int_re = re.compile(r'^\d+$')
star_or_int_re = re.compile(r'^(\d+|\*)$')
special_weekday_re = re.compile(r'^(\w+)#(\d+)|l(\d+)$')
hash_expression_re = re.compile(
    r'^(?P<hash_type>h|r)(\((?P<range_begin>\d+)-(?P<range_end>\d+)\))?(\/(?P<divisor>\d+))?$'
)
VALID_LEN_EXPRESSION = [5, 6]


def timedelta_to_seconds(td):
    return (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10 ** 6) \
           / 10 ** 6


def datetime_to_timestamp(d):
    if d.tzinfo is not None:
        d = d.replace(tzinfo=None) - d.utcoffset()

    return timedelta_to_seconds(d - datetime.datetime(1970, 1, 1))


def _get_caller_globals_and_locals():
    """
    Returns the globals and locals of the calling frame.

    Is there an alternative to frame hacking here?
    """
    caller_frame = inspect.stack()[2]
    myglobals = caller_frame[0].f_globals
    mylocals = caller_frame[0].f_locals
    return myglobals, mylocals


class CroniterError(ValueError):
    """ General top-level Croniter base exception """
    pass


class CroniterBadTypeRangeError(TypeError):
    """."""


class CroniterBadCronError(CroniterError):
    """ Syntax, unknown value, or range error within a cron expression """
    pass


class CroniterUnsupportedSyntaxError(CroniterBadCronError):
    """ Valid cron syntax, but likely to produce inaccurate results """
    # Extending CroniterBadCronError, which may be contridatory, but this allows
    # catching both errors with a single exception.  From a user perspective
    # these will likely be handled the same way.
    pass


class CroniterBadDateError(CroniterError):
    """ Unable to find next/prev timestamp match """
    pass


class CroniterNotAlphaError(CroniterBadCronError):
    """ Cron syntax contains an invalid day or month abbreviation """
    pass


class croniter(object):
    MONTHS_IN_YEAR = 12
    RANGES = (
        (0, 59),
        (0, 23),
        (1, 31),
        (1, 12),
        (0, 7),
        (0, 59)
    )
    DAYS = (
        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
    )

    ALPHACONV = (
        {},  # 0: min
        {},  # 1: hour
        {"l": "l"},  # 2: dom
        # 3: mon
        {'jan': 1, 'feb': 2, 'mar': 3, 'apr': 4, 'may': 5, 'jun': 6,
         'jul': 7, 'aug': 8, 'sep': 9, 'oct': 10, 'nov': 11, 'dec': 12},
        # 4: dow
        {'sun': 0, 'mon': 1, 'tue': 2, 'wed': 3, 'thu': 4, 'fri': 5, 'sat': 6},
        # command/user
        {}
    )

    LOWMAP = (
        {},
        {},
        {0: 1},
        {0: 1},
        {7: 0},
        {},
    )

    LEN_MEANS_ALL = (
        60,
        24,
        31,
        12,
        7,
        60
    )

    bad_length = 'Exactly 5 or 6 columns has to be specified for iterator ' \
                 'expression.'

    minute = None
    hour = None
    day_of_week = None
    day_of_month = None
    month_of_year = None

    def __init__(self, expr_format, start_time=None, ret_type=float,
                 day_or=True, max_years_between_matches=None, is_prev=False,
                 hash_id=None):
        self._ret_type = ret_type
        self._day_or = day_or

        if hash_id:
            if not isinstance(hash_id, (bytes, str)):
                raise TypeError('hash_id must be bytes or UTF-8 string')
            if not isinstance(hash_id, bytes):
                hash_id = hash_id.encode('UTF-8')

        self._max_years_btw_matches_explicitly_set = (
                max_years_between_matches is not None)
        if not self._max_years_btw_matches_explicitly_set:
            max_years_between_matches = 50
        self._max_years_between_matches = max(int(max_years_between_matches), 1)

        if start_time is None:
            start_time = time()

        self.tzinfo = None

        self.start_time = None
        self.dst_start_time = None
        self.cur = None
        self.set_current(start_time, force=False)

        self.expanded, self.nth_weekday_of_month = self.expand(expr_format, hash_id=hash_id)
        self._is_prev = is_prev

    @classmethod
    def _alphaconv(cls, index, key, expressions):
        try:
            return cls.ALPHACONV[index][key]
        except KeyError:
            raise CroniterNotAlphaError(
                "[{0}] is not acceptable".format(" ".join(expressions)))

    def get_next(self, ret_type=None, start_time=None):
        self.set_current(start_time, force=True)
        return self._get_next(ret_type or self._ret_type, is_prev=False)

    def get_prev(self, ret_type=None):
        return self._get_next(ret_type or self._ret_type, is_prev=True)

    def get_current(self, ret_type=None):
        ret_type = ret_type or self._ret_type
        if issubclass(ret_type, datetime.datetime):
            return self._timestamp_to_datetime(self.cur)
        return self.cur

    def set_current(self, start_time, force=True):
        if (force or (self.cur is None)) and start_time is not None:
            if isinstance(start_time, datetime.datetime):
                self.tzinfo = start_time.tzinfo
                start_time = self._datetime_to_timestamp(start_time)

            self.start_time = start_time
            self.dst_start_time = start_time
            self.cur = start_time
        return self.cur

    @classmethod
    def _datetime_to_timestamp(cls, d):
        """
        Converts a `datetime` object `d` into a UNIX timestamp.
        """
        return datetime_to_timestamp(d)

    def _timestamp_to_datetime(self, timestamp):
        """
        Converts a UNIX timestamp `timestamp` into a `datetime` object.
        """
        result = datetime.datetime.utcfromtimestamp(timestamp)
        if self.tzinfo:
            result = result.replace(tzinfo=tzutc()).astimezone(self.tzinfo)

        return result

    @classmethod
    def _timedelta_to_seconds(cls, td):
        """
        Converts a 'datetime.timedelta' object `td` into seconds contained in
        the duration.
        Note: We cannot use `timedelta.total_seconds()` because this is not
        supported by Python 2.6.
        """
        return timedelta_to_seconds(td)

    def _get_next(self, ret_type=None, start_time=None, is_prev=None):
        self.set_current(start_time, force=True)
        if is_prev is None:
            is_prev = self._is_prev
        self._is_prev = is_prev
        expanded = self.expanded[:]
        nth_weekday_of_month = self.nth_weekday_of_month.copy()

        ret_type = ret_type or self._ret_type

        if not issubclass(ret_type, (float, datetime.datetime)):
            raise TypeError("Invalid ret_type, only 'float' or 'datetime' "
                            "is acceptable.")

        # exception to support day of month and day of week as defined in cron
        if (expanded[2][0] != '*' and expanded[4][0] != '*') and self._day_or:
            bak = expanded[4]
            expanded[4] = ['*']
            t1 = self._calc(self.cur, expanded, nth_weekday_of_month, is_prev)
            expanded[4] = bak
            expanded[2] = ['*']

            t2 = self._calc(self.cur, expanded, nth_weekday_of_month, is_prev)
            if not is_prev:
                result = t1 if t1 < t2 else t2
            else:
                result = t1 if t1 > t2 else t2
        else:
            result = self._calc(self.cur, expanded,
                                nth_weekday_of_month, is_prev)

        # DST Handling for cron job spanning across days
        dtstarttime = self._timestamp_to_datetime(self.dst_start_time)
        dtstarttime_utcoffset = (
                dtstarttime.utcoffset() or datetime.timedelta(0))
        dtresult = self._timestamp_to_datetime(result)
        lag = lag_hours = 0
        # do we trigger DST on next crontab (handle backward changes)
        dtresult_utcoffset = dtstarttime_utcoffset
        if dtresult and self.tzinfo:
            dtresult_utcoffset = dtresult.utcoffset()
            lag_hours = (
                    self._timedelta_to_seconds(dtresult - dtstarttime) / (60 * 60)
            )
            lag = self._timedelta_to_seconds(
                dtresult_utcoffset - dtstarttime_utcoffset
            )
        hours_before_midnight = 24 - dtstarttime.hour
        if dtresult_utcoffset != dtstarttime_utcoffset:
            if (
                    (lag > 0 and abs(lag_hours) >= hours_before_midnight)
                    or (lag < 0 and
                        ((3600 * abs(lag_hours) + abs(lag)) >= hours_before_midnight * 3600))
            ):
                dtresult_adjusted = dtresult - datetime.timedelta(seconds=lag)
                result_adjusted = self._datetime_to_timestamp(dtresult_adjusted)
                # Do the actual adjust only if the result time actually exists
                if self._timestamp_to_datetime(result_adjusted).tzinfo == dtresult_adjusted.tzinfo:
                    dtresult = dtresult_adjusted
                    result = result_adjusted
                self.dst_start_time = result
        self.cur = result
        if issubclass(ret_type, datetime.datetime):
            result = dtresult
        return result

    # iterator protocol, to enable direct use of croniter
    # objects in a loop, like "for dt in croniter('5 0 * * *'): ..."
    # or for combining multiple croniters into single
    # dates feed using 'itertools' module
    def all_next(self, ret_type=None):
        '''Generator of all consecutive dates. Can be used instead of
        implicit call to __iter__, whenever non-default
        'ret_type' has to be specified.
        '''
        # In a Python 3.7+ world:  contextlib.suppress and contextlib.nullcontext could be used instead
        try:
            while True:
                self._is_prev = False
                yield self._get_next(ret_type or self._ret_type)
        except CroniterBadDateError:
            if self._max_years_btw_matches_explicitly_set:
                return
            else:
                raise

    def all_prev(self, ret_type=None):
        '''Generator of all previous dates.'''
        try:
            while True:
                self._is_prev = True
                yield self._get_next(ret_type or self._ret_type)
        except CroniterBadDateError:
            if self._max_years_btw_matches_explicitly_set:
                return
            else:
                raise

    def iter(self, *args, **kwargs):
        return (self._is_prev and self.all_prev or self.all_next)

    def __iter__(self):
        return self

    __next__ = next = _get_next

    def _calc(self, now, expanded, nth_weekday_of_month, is_prev):
        if is_prev:
            now = math.ceil(now)
            nearest_diff_method = self._get_prev_nearest_diff
            sign = -1
            offset = (len(expanded) == 6 or now % 60 > 0) and 1 or 60
        else:
            now = math.floor(now)
            nearest_diff_method = self._get_next_nearest_diff
            sign = 1
            offset = (len(expanded) == 6) and 1 or 60

        dst = now = self._timestamp_to_datetime(now + sign * offset)

        month, year = dst.month, dst.year
        current_year = now.year
        DAYS = self.DAYS

        def proc_month(d):
            try:
                expanded[3].index('*')
            except ValueError:
                diff_month = nearest_diff_method(
                    d.month, expanded[3], self.MONTHS_IN_YEAR)
                days = DAYS[month - 1]
                if month == 2 and self.is_leap(year) is True:
                    days += 1

                reset_day = 1

                if diff_month is not None and diff_month != 0:
                    if is_prev:
                        d += relativedelta(months=diff_month)
                        reset_day = DAYS[d.month - 1]
                        d += relativedelta(
                            day=reset_day, hour=23, minute=59, second=59)
                    else:
                        d += relativedelta(months=diff_month, day=reset_day,
                                           hour=0, minute=0, second=0)
                    return True, d
            return False, d

        def proc_day_of_month(d):
            try:
                expanded[2].index('*')
            except ValueError:
                days = DAYS[month - 1]
                if month == 2 and self.is_leap(year) is True:
                    days += 1
                if 'l' in expanded[2] and days == d.day:
                    return False, d

                if is_prev:
                    days_in_prev_month = DAYS[
                        (month - 2) % self.MONTHS_IN_YEAR]
                    diff_day = nearest_diff_method(
                        d.day, expanded[2], days_in_prev_month)
                else:
                    diff_day = nearest_diff_method(d.day, expanded[2], days)

                if diff_day is not None and diff_day != 0:
                    if is_prev:
                        d += relativedelta(
                            days=diff_day, hour=23, minute=59, second=59)
                    else:
                        d += relativedelta(
                            days=diff_day, hour=0, minute=0, second=0)
                    return True, d
            return False, d

        def proc_day_of_week(d):
            try:
                expanded[4].index('*')
            except ValueError:
                diff_day_of_week = nearest_diff_method(
                    d.isoweekday() % 7, expanded[4], 7)
                if diff_day_of_week is not None and diff_day_of_week != 0:
                    if is_prev:
                        d += relativedelta(days=diff_day_of_week,
                                           hour=23, minute=59, second=59)
                    else:
                        d += relativedelta(days=diff_day_of_week,
                                           hour=0, minute=0, second=0)
                    return True, d
            return False, d

        def proc_day_of_week_nth(d):
            if '*' in nth_weekday_of_month:
                s = nth_weekday_of_month['*']
                for i in range(0, 7):
                    if i in nth_weekday_of_month:
                        nth_weekday_of_month[i].update(s)
                    else:
                        nth_weekday_of_month[i] = s
                del nth_weekday_of_month['*']

            candidates = []
            for wday, nth in nth_weekday_of_month.items():
                c = self._get_nth_weekday_of_month(d.year, d.month, wday)
                for n in nth:
                    if n == "l":
                        candidate = c[-1]
                    elif len(c) < n:
                        continue
                    else:
                        candidate = c[n - 1]
                    if (
                            (is_prev and candidate <= d.day) or
                            (not is_prev and d.day <= candidate)
                    ):
                        candidates.append(candidate)

            if not candidates:
                if is_prev:
                    d += relativedelta(days=-d.day,
                                       hour=23, minute=59, second=59)
                else:
                    days = DAYS[month - 1]
                    if month == 2 and self.is_leap(year) is True:
                        days += 1
                    d += relativedelta(days=(days - d.day + 1),
                                       hour=0, minute=0, second=0)
                return True, d

            candidates.sort()
            diff_day = (candidates[-1] if is_prev else candidates[0]) - d.day
            if diff_day != 0:
                if is_prev:
                    d += relativedelta(days=diff_day,
                                       hour=23, minute=59, second=59)
                else:
                    d += relativedelta(days=diff_day,
                                       hour=0, minute=0, second=0)
                return True, d
            return False, d

        def proc_hour(d):
            try:
                expanded[1].index('*')
            except ValueError:
                diff_hour = nearest_diff_method(d.hour, expanded[1], 24)
                if diff_hour is not None and diff_hour != 0:
                    if is_prev:
                        d += relativedelta(
                            hours=diff_hour, minute=59, second=59)
                    else:
                        d += relativedelta(hours=diff_hour, minute=0, second=0)
                    return True, d
            return False, d

        def proc_minute(d):
            try:
                expanded[0].index('*')
            except ValueError:
                diff_min = nearest_diff_method(d.minute, expanded[0], 60)
                if diff_min is not None and diff_min != 0:
                    if is_prev:
                        d += relativedelta(minutes=diff_min, second=59)
                    else:
                        d += relativedelta(minutes=diff_min, second=0)
                    return True, d
            return False, d

        def proc_second(d):
            if len(expanded) == 6:
                try:
                    expanded[5].index('*')
                except ValueError:
                    diff_sec = nearest_diff_method(d.second, expanded[5], 60)
                    if diff_sec is not None and diff_sec != 0:
                        d += relativedelta(seconds=diff_sec)
                        return True, d
            else:
                d += relativedelta(second=0)
            return False, d

        procs = [proc_month,
                 proc_day_of_month,
                 (proc_day_of_week_nth if nth_weekday_of_month
                  else proc_day_of_week),
                 proc_hour,
                 proc_minute,
                 proc_second]

        while abs(year - current_year) <= self._max_years_between_matches:
            next = False
            for proc in procs:
                (changed, dst) = proc(dst)
                if changed:
                    month, year = dst.month, dst.year
                    next = True
                    break
            if next:
                continue
            return self._datetime_to_timestamp(dst.replace(microsecond=0))

        if is_prev:
            raise CroniterBadDateError("failed to find prev date")
        raise CroniterBadDateError("failed to find next date")

    def _get_next_nearest(self, x, to_check):
        small = [item for item in to_check if item < x]
        large = [item for item in to_check if item >= x]
        large.extend(small)
        return large[0]

    def _get_prev_nearest(self, x, to_check):
        small = [item for item in to_check if item <= x]
        large = [item for item in to_check if item > x]
        small.reverse()
        large.reverse()
        small.extend(large)
        return small[0]

    def _get_next_nearest_diff(self, x, to_check, range_val):
        for i, d in enumerate(to_check):
            if d == "l":
                # if 'l' then it is the last day of month
                # => its value of range_val
                d = range_val
            if d >= x:
                return d - x
        return to_check[0] - x + range_val

    def _get_prev_nearest_diff(self, x, to_check, range_val):
        candidates = to_check[:]
        candidates.reverse()
        for d in candidates:
            if d != 'l' and d <= x:
                return d - x
        if 'l' in candidates:
            return -x
        candidate = candidates[0]
        for c in candidates:
            # fixed: c < range_val
            # this code will reject all 31 day of month, 12 month, 59 second,
            # 23 hour and so on.
            # if candidates has just a element, this will not harmful.
            # but candidates have multiple elements, then values equal to
            # range_val will rejected.
            if c <= range_val:
                candidate = c
                break
        if candidate > range_val:
            # fix crontab "0 6 30 3 *" condidates only a element,
            # then get_prev error return 2021-03-02 06:00:00
            return - x
        return (candidate - x - range_val)

    @staticmethod
    def _get_nth_weekday_of_month(year, month, day_of_week):
        """ For a given year/month return a list of days in nth-day-of-month order.
        The last weekday of the month is always [-1].
        """
        w = (day_of_week + 6) % 7
        c = calendar.Calendar(w).monthdayscalendar(year, month)
        if c[0][0] == 0:
            c.pop(0)
        return tuple(i[0] for i in c)

    def is_leap(self, year):
        if year % 400 == 0 or (year % 4 == 0 and year % 100 != 0):
            return True
        else:
            return False

    @classmethod
    def _expand(cls, expr_format, hash_id=None):
        # Split the expression in components, and normalize L -> l, MON -> mon,
        # etc. Keep expr_format untouched so we can use it in the exception
        # messages.
        expr_aliases = {
            '@midnight': ('0 0 * * *', 'h h(0-2) * * * h'),
            '@hourly': ('0 * * * *', 'h * * * * h'),
            '@daily': ('0 0 * * *', 'h h * * * h'),
            '@weekly': ('0 0 * * 0', 'h h * * h h'),
            '@monthly': ('0 0 1 * *', 'h h h * * h'),
            '@yearly': ('0 0 1 1 *', 'h h h h * h'),
            '@annually': ('0 0 1 1 *', 'h h h h * h'),
        }

        efl = expr_format.lower()
        hash_id_expr = hash_id is not None and 1 or 0
        try:
            efl = expr_aliases[efl][hash_id_expr]
        except KeyError:
            pass

        expressions = efl.split()

        if len(expressions) not in VALID_LEN_EXPRESSION:
            raise CroniterBadCronError(cls.bad_length)

        expanded = []
        nth_weekday_of_month = {}

        for i, expr in enumerate(expressions):
            if i == 0:
                cls.minute = expr
            if i == 1:
                cls.hour = expr
            if i == 2:
                cls.day_of_week = expr
            if i == 3:
                cls.day_of_month = expr
            if i == 4:
                cls.month_of_year = expr
            for expanderid, expander in EXPANDERS.items():
                expr = expander(cls).expand(efl, i, expr, hash_id=hash_id)

            e_list = expr.split(',')
            res = []

            while len(e_list) > 0:
                e = e_list.pop()

                if i == 4:
                    # Handle special case in the day-of-week expression
                    m = special_weekday_re.match(str(e))
                    if m:
                        orig_e = e
                        e, nth, last = m.groups()
                        if nth:
                            try:
                                nth = int(nth)
                                assert (nth >= 1 and nth <= 5)
                            except (ValueError, AssertionError):
                                raise CroniterBadCronError(
                                    "[{0}] is not acceptable.  Invalid day_of_week "
                                    "value: '{1}'".format(expr_format, orig_e))
                        elif last:
                            nth = "l"
                            e = last
                        del last, orig_e
                    else:
                        nth = None

                # Before matching step_search_re, normalize "*" to "{min}-{max}".
                # Example: in the minute field, "*/5" normalizes to "0-59/5"
                t = re.sub(r'^\*(\/.+)$', r'%d-%d\1' % (
                    cls.RANGES[i][0],
                    cls.RANGES[i][1]),
                           str(e))
                m = step_search_re.search(t)

                if not m:
                    # Before matching step_search_re,
                    # normalize "{start}/{step}" to "{start}-{max}/{step}".
                    # Example: in the minute field, "10/5" normalizes to "10-59/5"
                    t = re.sub(r'^(.+)\/(.+)$', r'\1-%d/\2' % (
                        cls.RANGES[i][1]),
                               str(e))
                    m = step_search_re.search(t)

                if m:
                    # early abort if low/high are out of bounds

                    (low, high, step) = m.group(1), m.group(2), m.group(4) or 1
                    if i == 2 and high == 'l':
                        high = '31'

                    if not only_int_re.search(low):
                        low = "{0}".format(cls._alphaconv(i, low, expressions))

                    if not only_int_re.search(high):
                        high = "{0}".format(cls._alphaconv(i, high, expressions))

                    if (
                            not low or not high or int(low) > int(high)
                            or not only_int_re.search(str(step))
                    ):
                        if i == 4 and high == '0':
                            # handle -Sun notation -> 7
                            high = '7'
                        else:
                            raise CroniterBadCronError(
                                "[{0}] is not acceptable".format(expr_format))

                    low, high, step = map(int, [low, high, step])
                    if (
                            max(low, high) > max(cls.RANGES[i][0], cls.RANGES[i][1])
                    ):
                        raise CroniterBadCronError(
                            "{0} is out of bands".format(expr_format))
                    try:
                        rng = range(low, high + 1, step)
                    except ValueError as exc:
                        raise CroniterBadCronError(
                            'invalid range: {0}'.format(exc))
                    e_list += (["{0}#{1}".format(item, nth) for item in rng]
                               if i == 4 and nth and nth != "l" else rng)
                else:
                    if t.startswith('-'):
                        raise CroniterBadCronError((
                                                       "[{0}] is not acceptable,"
                                                       "negative numbers not allowed"
                                                   ).format(expr_format))
                    if not star_or_int_re.search(t):
                        t = cls._alphaconv(i, t, expressions)

                    try:
                        t = int(t)
                    except ValueError:
                        pass

                    if t in cls.LOWMAP[i] and not (
                            # do not support 0 as a month either for classical 5 fields cron
                            # or 6fields second repeat form
                            # but still let conversion happen if day field is shifted
                            (i in [2, 3] and len(expressions) == 5) or
                            (i in [3, 4] and len(expressions) == 6)
                    ):
                        t = cls.LOWMAP[i][t]

                    if (
                            t not in ["*", "l"]
                            and (int(t) < cls.RANGES[i][0] or
                                 int(t) > cls.RANGES[i][1])
                    ):
                        raise CroniterBadCronError(
                            "[{0}] is not acceptable, out of range".format(
                                expr_format))

                    res.append(t)

                    if i == 4 and nth:
                        if t not in nth_weekday_of_month:
                            nth_weekday_of_month[t] = set()
                        nth_weekday_of_month[t].add(nth)

            res = set(res)
            res = sorted(res, key=lambda i: "{:02}".format(i) if isinstance(i, int) else i)
            if len(res) == cls.LEN_MEANS_ALL[i]:
                res = ['*']

            expanded.append(['*'] if (len(res) == 1
                                      and res[0] == '*')
                            else res)

        # Check to make sure the dow combo in use is supported
        if nth_weekday_of_month:
            dow_expanded_set = set(expanded[4])
            dow_expanded_set = dow_expanded_set.difference(nth_weekday_of_month.keys())
            dow_expanded_set.discard("*")
            if dow_expanded_set:
                raise CroniterUnsupportedSyntaxError(
                    "day-of-week field does not support mixing literal values and nth day of week syntax.  "
                    "Cron: '{}'    dow={} vs nth={}".format(expr_format, dow_expanded_set, nth_weekday_of_month))

        return expanded, nth_weekday_of_month

    @classmethod
    def expand(cls, expr_format, hash_id=None):
        """Shallow non Croniter ValueError inside a nice CroniterBadCronError"""
        try:
            return cls._expand(expr_format, hash_id=hash_id)
        except ValueError as exc:
            error_type, error_instance, traceback = sys.exc_info()
            if isinstance(exc, CroniterError):
                raise
            if int(sys.version[0]) >= 3:
                globs, locs = _get_caller_globals_and_locals()
                exec("raise CroniterBadCronError from  exc", globs, locs)
            else:
                raise CroniterBadCronError("{0}".format(exc))

    @classmethod
    def is_valid(cls, expression, hash_id=None):
        try:
            cls.expand(expression, hash_id=hash_id)
        except CroniterError:
            return False
        else:
            return True

    @classmethod
    def match(cls, cron_expression, testdate, day_or=True):
        cron = cls(cron_expression, testdate, ret_type=datetime.datetime, day_or=day_or)
        td, ms1 = cron.get_current(datetime.datetime), relativedelta(microseconds=1)
        if not td.microsecond:
            td = td + ms1
        cron.set_current(td, force=True)
        tdp, tdt = cron.get_current(), cron.get_prev()
        return (max(tdp, tdt) - min(tdp, tdt)).total_seconds() < 60


def croniter_range(start, stop, expr_format, ret_type=None, day_or=True, exclude_ends=False,
                   _croniter=None):
    """
    Generator that provides all times from start to stop matching the given cron expression.
    If the cron expression matches either 'start' and/or 'stop', those times will be returned as
    well unless 'exclude_ends=True' is passed.

    You can think of this function as sibling to the builtin range function for datetime objects.
    Like range(start,stop,step), except that here 'step' is a cron expression.
    """
    _croniter = _croniter or croniter
    auto_rt = datetime.datetime
    # type is used in first if branch for perfs reasons
    if (
            type(start) != type(stop) and not (
            isinstance(start, type(stop)) or
            isinstance(stop, type(start)))
    ):
        raise CroniterBadTypeRangeError(
            "The start and stop must be same type.  {0} != {1}".
            format(type(start), type(stop)))
    if isinstance(start, (float, int)):
        start, stop = (datetime.datetime.utcfromtimestamp(t) for t in (start, stop))
        auto_rt = float
    if ret_type is None:
        ret_type = auto_rt
    if not exclude_ends:
        ms1 = relativedelta(microseconds=1)
        if start < stop:  # Forward (normal) time order
            start -= ms1
            stop += ms1
        else:  # Reverse time order
            start += ms1
            stop -= ms1
    year_span = math.floor(abs(stop.year - start.year)) + 1
    ic = _croniter(expr_format, start, ret_type=datetime.datetime, day_or=day_or,
                   max_years_between_matches=year_span)
    # define a continue (cont) condition function and step function for the main while loop
    if start < stop:  # Forward
        def cont(v):
            return v < stop

        step = ic.get_next
    else:  # Reverse
        def cont(v):
            return v > stop

        step = ic.get_prev
    try:
        dt = step()
        while cont(dt):
            if ret_type is float:
                yield ic.get_current(float)
            else:
                yield dt
            dt = step()
    except CroniterBadDateError:
        # Stop iteration when this exception is raised; no match found within the given year range
        return


class HashExpander:

    def __init__(self, cronit):
        self.cron = cronit

    def do(self, idx, hash_type="h", hash_id=None, range_end=None, range_begin=None):
        """Return a hashed/random integer given range/hash information"""
        if range_end is None:
            range_end = self.cron.RANGES[idx][1]
        if range_begin is None:
            range_begin = self.cron.RANGES[idx][0]
        if hash_type == 'r':
            crc = random.randint(0, 0xFFFFFFFF)
        else:
            crc = binascii.crc32(hash_id) & 0xFFFFFFFF
        return ((crc >> idx) % (range_end - range_begin + 1)) + range_begin

    def match(self, efl, idx, expr, hash_id=None, **kw):
        return hash_expression_re.match(expr)

    def expand(self, efl, idx, expr, hash_id=None, match='', **kw):
        """Expand a hashed/random expression to its normal representation"""
        if match == '':
            match = self.match(efl, idx, expr, hash_id, **kw)
        if not match:
            return expr
        m = match.groupdict()

        if m['hash_type'] == 'h' and hash_id is None:
            raise CroniterBadCronError('Hashed definitions must include hash_id')

        if m['range_begin'] and m['range_end'] and m['divisor']:
            # Example: H(30-59)/10 -> 34-59/10 (i.e. 34,44,54)
            if int(m["divisor"]) == 0:
                raise CroniterBadCronError("Bad expression: {0}".format(expr))

            return '{0}-{1}/{2}'.format(
                self.do(
                    idx,
                    hash_type=m['hash_type'],
                    hash_id=hash_id,
                    range_end=int(m['divisor']),
                ) + int(m['range_begin']),
                int(m['range_end']),
                int(m['divisor']),
            )
        elif m['range_begin'] and m['range_end']:
            # Example: H(0-29) -> 12
            return str(
                self.do(
                    idx,
                    hash_type=m['hash_type'],
                    hash_id=hash_id,
                    range_end=int(m['range_end']),
                    range_begin=int(m['range_begin']),
                )
            )
        elif m['divisor']:
            # Example: H/15 -> 7-59/15 (i.e. 7,22,37,52)
            if int(m["divisor"]) == 0:
                raise CroniterBadCronError("Bad expression: {0}".format(expr))

            return '{0}-{1}/{2}'.format(
                self.do(
                    idx,
                    hash_type=m['hash_type'],
                    hash_id=hash_id,
                    range_end=int(m['divisor']),
                ),
                self.cron.RANGES[idx][1],
                int(m['divisor']),
            )
        else:
            # Example: H -> 32
            return str(
                self.do(
                    idx,
                    hash_type=m['hash_type'],
                    hash_id=hash_id,
                )
            )


EXPANDERS = OrderedDict([
    ('hash', HashExpander),
])
